Method for fabricating an insulating film from a silicone resin using O.sub.

Abstract

A silicone resin is applied on a substrate to form a coating film. The coating film is subjected to a reactive ion etching in an atmosphere containing at least O 2 . Thus, the film is inorganized in its surface and has a distribution of the residue, an organic radical, contained therein gradually increasing in the depth thereof. This permits an insulating film having excellent heat endurance to be formed without generation of any cracks. This insulating film is very useful as an interlayer insulating film for multi-layer wiring.

We claim: 
     
       1. A method for fabricating an insulating film comprising the steps of (a) applying silicone resin having a repeating siloxane bond as a main chain and a methyl side radical on a substrate to form an coating film thereon, said substrate having a first level wiring pattern thereon;   (b) baking said substrate at a temperature where said coating film is not resolved thereby to solidify said coating film;   (c) subjecting the surface of said coating film to a reactive ion etching in an atmosphere containing at least O 2  at a gas pressure of 10-400 m Torr so that the surface of said coating film becomes inorganic and also the residue of an organic radical contained in the coating film is distributed to gradually increase in the depth direction of said coating film;   (d) forming a photoresist film having a predetermined pattern on said coating film;   (e) removing an exposed portion of said coating film to form a hole so that a part of surface of said first level wiring pattern is exposed through the hole; and   (f) forming a second level wiring pattern which is connected electrically to said first level wiring pattern through said hole and extending onto a surface of said coating film.   
     
     
       2. A method of fabricating an insulating film according to claim 1, further comprising the steps successive to the step (c) of (d) forming a hole at a predetermined position of said coating film; and   (e) subjecting the exposed inner side wall of said hole to the reactive ion etching in an atmosphere containing at least O 2  so that the surface of the side wall is inorganized.   
     
     
       3. A method for fabricating an insulating film according to claim 2, wherein said reactive ion etching in step (e) is carried out in an atmosphere containing at least O 2  at the gas pressure of 10-400 m Torr. 
     
     
       4. A method of fabricating an insulating film according to claim 1, wherein said reactive ion etching is carried out using a parallel plate type ion etching reactor. 
     
     
       5. A method for fabricating an insulating film according to claim 1, wherein said reactive ion etching is carried out using a microwave plasma etching apparatus. 
     
     
       6. A method for fabricating an insulating film according to claim 1, wherein said atmosphere contains at least one selected from the group consisting of O 2 , CO, CO 2 , NO, and NO 2 . 
     
     
       7. A method for fabricating an insulating film according to claim 6, wherein said atmosphere further contains at least one of N 2  and CF 4 . 
     
     
       8. A method for fabricating an insulating film according to claim 1, further comprising the step of forming a hole in said coating film previously to the step of (c), wherein the surface of said application film and the side wall surface of said hole are inorganized in the step of (c). 
     
     
       9. A method for fabricating an insulating film according to claim 8, wherein said reactive ion etching is carried out using a parallel plate type ion etching reactor. 
     
     
       10. A method for fabricating an insulation film according to claim 8, wherein said reactive ion etching is carried out using a microwave plasma etching apparatus. 
     
     
       11. A method for fabricating an insulating film according to claim 8, wherein said atmosphere contains at least one selected from the group consisting of O 2 , CO, CO 2 , NO and NO 2 . 
     
     
       12. A method for fabricating an insulating film according to claim 11, wherein said atmosphere further contains at least one of N 2  and CF 4 . 
     
     
       13. A method for fabricating an insulating film according to claim 1, wherein said reactive ion etching is carried out in such a state that said substrate is placed on a susceptor made of graphite. 
     
     
       14. A method for fabricating an insulating film according to claim 8, wherein said reactive ion etching is carried out in such a state that said substrate is placed on a susceptor made of graphite. 
     
     
       15. A method for fabricating an interlayer insulating film in a multi-layer wiring comprising: applying silicone resin having a repeating siloxane bond as a main chain and a methyl side radical on a substrate having a first level wiring pattern thereon to form a coating film;   baking said coating film at a temperature at which said coating film is not resolved to form a solidified coating film;   subjecting an exposed surface of said solidified coating film to a reactive ion etching in an atmosphere containing at least O 2  at a gas pressure of 10-400 m Torr so that said exposed surface of said solidified coating film becomes inorganic and also that residue of an organic radical contained in said coating film is distributed to gradually increase in the depth direction of said coating film;   forming a hole at a predetermined position of said solidified coating film; and   forming a second level wiring pattern over said exposed surface of said solidified coating film which has been inorganized such that said first level wiring pattern and said second level wiring pattern electrically connect through said hole.   
     
     
       16. A method for fabricating an interlayer insulating film in a multilayer wiring according to claim 15, wherein said coating film has a thickness of at least 0.4 μm. 
     
     
       17. A method for fabricating an interlayer insulating film in a multilayer wiring according to claim 15, wherein said coating film has a thickness of at least 0.6 μm. 
     
     
       18. A method for fabricating an interlayer insulating film in a multilayer wiring according to claim 15, wherein said hole is formed before subjecting said exposed surface of said solidified coating film to said reactive ion etching. 
     
     
       19. A method for fabricating an interlayer insulating film in a multilayer wiring according to claim 15, wherein said hole is formed after subjecting said exposed surface of said solidified coating film to said reactive ion etching, and an exposed inner side wall of said hole is subjected to reactive ion etching in an atmosphere containing at least O 2  so that said exposed inner side wall surface is inorganized. 
     
     
       20. A method for fabricating an interlayer insulating film in a multilayer wiring according to claim 15, wherein said hole is formed by providing a photoresist film having a predetermined pattern on said solidified coating film and removing a portion of said solidified coating film exposed through said predetermined pattern, and wherein said photoresist film is removed by a O 2  plasma ashing treatment prior to forming said second level wiring pattern. 
     
     
       21. A method for fabricating an insulating film comprising the steps of (a) forming a coating film having a (Si-O) n  bond as a main chain and a methyl side radical on a substrate, said substrate having a first level wiring pattern thereon;   (b) baking said coating film;   (c) subjecting said coating film to a reactive ion etching in an atmosphere containing at least O 2  at a gas pressure if 10-100 m Torr in such a state that said substrate is placed on a susceptor made of graphite;   (d) forming a photoresist film having a predetermined pattern on said coating film;   (e) removing an exposed portion of said coating film to form a hole so that a part of surface of said first level wiring pattern is exposed through the hole; and   (f) forming a second level wiring pattern which is connected electrically to said first level wiring pattern through said hole and extending onto a surface of said coating film.   
     
     
       22. A method according to claim 21, wherein said coating film has a thickness of at least 0.4 μm. 
     
     
       23. A method according to claim 21, wherein said coating film has a thickness of at least 0.6 μm. 
     
     
       24. A method according to claim 1, wherein said coating film has a thickness of at least 0.4 μm. 
     
     
       25. A method according to claim 1, wherein said coating film has a thickness of at least 0.6 μm.